The immunohistochemical expression of DNA-PKCS and Ku (p70/p80) in head and neck cancers: Relationships with radiosensitivity

Purpose: The DNA-PK complex is one of the major pathways by which mammalian cells respond to DNA double-strand breaks induced by ionizing radiation. T his study evaluated the relationship between the immunohistochemical expres sion of the individual components of DNA-PK and cellular radiosensitivity i n head and neck cancers, Methods and Materials: Biopsies from patients with previously untreated squ amous cell carcinomas of the head and neck were assessed for inherent tumor radiosensitivity measured as the surviving fraction at 2 Gy (SF2) using a soft agar clonogenic assay. Paraffin-embedded tumor material from 64 Succes sfully grown specimens was immunohistochemically stained for expression of DNA-PKcs and Ku (p70/p80), The same tumor material was previously analyzed for the immunohistochemical expression of p53, Results: A significant correlation was found between the degree of expressi on of DNA-PKcs and Ku (p70/p80) (r = 0.55, p < 0.001). There were no overal l significant differences in the levels of expression of DNA-PKcs and Ku (p 70/p80) in tumors from patients of either sex, different sites, histologies , and stages. No relationship was found between SF, and the expression of e ither DNA-PKcs (r = 0.22, p = 0.081) or Ku (p70/p80) (r = 0.064, p 0.62), C omparison with previous immunohistochemical characterization showed no sign ificant correlations between the expression levels of p53 and either DNA-PK cs (r = 0.093,p = 0.46) or Ku (p70/p80) (p = -0.17,p 0.17). Conclusions: This study suggests that determining the immunohistochemical e xpression of DNA-PK in head and neck cancers from multiple sites does not h ave a role as a predictive assay of tumor irt vitro radiosensitivity. (C) 1 999 Elsevier Science Inc.